Abstract
Two kinds of spikes, a single-spike unit and burst unit, were obtained by a glass suction electrode recording from neurons in Auerbach's plexus of the guinea pig ileum. Both spikes were inhibited by tetrodotoxin but not by Mn2+. Frequency of the single-spike unit was increased by nicotine and high concentrations of acetylcholine. The single-spike unit induced by nicotine was inhibited by hexamethonium, while hexamethonium was without any effect on the spontaneous single-spike unit. Morphine inhibited the spontaneous single-spike unit. The spontaneous singlespike unit was also inhibited by α-adrenergic stimulants but not by β-adrenergic stimulants. Inhibition of single-spike unit activity by the α-adrenergic stimulants was antagonized by α-adrenergic blockers. These findings indicate that the single-spike unit is concerned with cholinergic transmission in Auerbach's plexus. The singlespike unit evoked by nicotine was partly inhibited by morphine or α-adrenergic stimulants. This fact indicated the possibility that morphine and the α-adrenergic stimulants also inhibit the acetylcholine release from the cholinergic nerve at the ending of the post-ganglionic fibres. On the other hand the burst unit was little affected by the drugs utilized herein.
